如何重置jquery datepicker onkeyup？

Question

我的jquery日期选择器完全按照预期工作，但我的问题是，如果从文本框中删除其中一个日期选择器，则日期计算框（CalcDate1）中的值应该消失。我的代码如下

<script type="text/javascript">
    $(function () {
        $('#datepicker7').datepicker({
            showOnFocus: false,
            showTrigger: '#calImg',
            beforeShowDay: $.datepicker.noWeekends,
            pickerClass: 'noPrevNext',
            dateFormat: "dd-mm-yy", changeMonth: true, changeYear: true,
            onClose: function (selectedDate) { $("#datepicker8").datepicker("option", "minDate", selectedDate) },
            onSelect: function (dateStr) {
                var min = $(this).datepicker('getDate');
                $('#datepicker8').datepicker('option', "calculateWeek", min);
                datepicked();
            }
        });
        $('#datepicker8').datepicker({
            showOnFocus: false,
            showTrigger: '#calImg',
            beforeShowDay: $.datepicker.noWeekends,
            pickerClass: 'noPrevNext',
            dateFormat: "dd-mm-yy", changeMonth: true, changeYear: true,
            onSelect: function (dateStr) {
                var max = $(this).datepicker('getDate');
                $('#datepicker7').datepicker('option', "calculateWeek", max);
                datepicked();
            }
        });
    });


    var datepicked = function () {
        var from = $('#datepicker7');
        var to = $('#datepicker8');
        var nights = $('#CalcDate1');

        var startDate = from.datepicker('getDate');
        startDate.setDate(startDate.getDate() + 1);

        var endDate = to.datepicker('getDate')

        // Validate input
        if (endDate && startDate) {
            // Calculate days between dates
            var millisecondsPerDay = 86400 * 1000; // Day in milliseconds
            startDate.setHours(0, 0, 0, 1);  // Start just after midnight
            endDate.setHours(23, 59, 59, 999);  // End just before midnight
            var diff = endDate - startDate;  // Milliseconds between datetime objects    
            var days = Math.ceil(diff / millisecondsPerDay);

            // Subtract two weekend days for every week in between
            var weeks = Math.floor(days / 7);
            var days = days - (weeks * 2);

            // Handle special cases
            var startDay = startDate.getDay();
            var endDay = endDate.getDay();

            // Remove weekend not previously removed.   
            if (startDay - endDay > 1)
                var days = days - 2;

            // Remove start day if span starts on Sunday but ends before Saturday
            if (startDay == 0 && endDay != 6)
                var days = days - 1

            // Remove end day if span ends on Saturday but starts after Sunday
            if (endDay == 6 && startDay != 0)
                var days = days - 1

            nights.val(days);
        }
    }
</script>

我将以下两段代码添加到他们的相对日期选择器中，但它们不起作用

keyup(function(e) {
    if(e.keyCode == 8 || e.keyCode == 46) {
        $.datepicker._clearDate(this);
        $( "#datepicker8" ).datepicker( "option", "minDate", "today" );
    }
});

keyup(function(e) {
        if(e.keyCode == 8 || e.keyCode == 46) {
            $.datepicker._clearDate(this);
            $( "#datepicker7" ).datepicker( "option", "maxDate", "" );
        }
    });

我的html助手是

<div class="form-group">
                                @Html.LabelFor(model => model.DateToAdvisors, "Date To Advisors", new { @class = "control-label col-md-5" })
                                <div class="col-md-offset-0">
                                    @Html.TextBoxFor(model => model.DateToAdvisors, new { @class = "datepicker7", id = "datepicker7" })
                                    @Html.ValidationMessageFor(model => model.DateToAdvisors)
                                </div>
                            </div>

<div class="form-group" style="padding-top:75px">
                                    @Html.LabelFor(model => model.ReplyFormAdvisors, "Reply From Advisors", new { @class = "control-label col-md-5" })
                                    <div class="col-md-offset-0">
                                        @Html.TextBoxFor(model => model.ReplyFormAdvisors, new { @class = "datepicker8", id = "datepicker8" })
                                        @Html.ValidationMessageFor(model => model.ReplyFormAdvisors)
                                    </div>
                            </div> 

<div class="form-group" style="padding-top:175px">
                                @Html.LabelFor(model => model.CalcDate1, "Date Calculated", new { @class = "control-label col-md-5" })
                                <div class="col-md-offset-0">
                                    @Html.TextBoxFor(model => model.CalcDate1)
                                    @Html.ValidationMessageFor(model => model.CalcDate1)
                                </div>
                            </div>